/home/r0/dav/atlas.dir/atlas3/sources/utilities/constants.h File Reference

#include <cstddef>
#include <limits>

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Namespaces
namespace	atlas
namespace	atlas::constants
Classes
class	atlas::constants::BaseShift< n >
	Computes (in the constant BaseShift<n>::value) the base two logarithm of n. More...
class	atlas::constants::BaseShift< 1ul >
class	atlas::constants::Bool< n >
	Tests whether n is non-zero. More...
class	atlas::constants::Bool<(size_t) 0ul >
Variables
const unsigned char	ucharMax = std::numeric_limits<unsigned char>::max()
const unsigned long	ulongMax = std::numeric_limits<unsigned long>::max()
const unsigned long	charBits = std::numeric_limits<unsigned char>::digits
const unsigned long	longBits = std::numeric_limits<unsigned long>::digits
const unsigned long	sizeBits = std::numeric_limits<size_t>::digits
const unsigned long	hiBit = 1ul << (longBits - 1)
const unsigned long	firstCharMask = (1ul << charBits) - 1ul
const size_t	RANK_MAX = 16ul
const unsigned long	posBits = longBits - 1ul
const unsigned long	baseBits = ~posBits
const unsigned long	baseShift = BaseShift<longBits>::value
	This one tells by how much we have to shift a binary number N to get the base (number of machine words needed for a bitmap of size N).

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Detailed Description

This is constants.h

Definition in file constants.h.

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Variable Documentation

const unsigned long atlas::constants::baseBits = ~posBits

Constant used to pick a bit-address apart: this is the logical complement of posBits. It is assumed that the number of bits in an unsigned long is a power of two. Definition at line 105 of file constants.h.

const unsigned long atlas::constants::baseShift = BaseShift<longBits>::value

This one tells by how much we have to shift a binary number N to get the base (number of machine words needed for a bitmap of size N). It is the base 2 logarithm of longBits. The difficulty is to compute this at compile time! We use a neat (and well-known) template trick for that. The result is correct only when n is a power of two. (Should be 5 on 32 bit machine.) Definition at line 133 of file constants.h. Referenced by atlas::bitmap::BitMap::BitMap().

const unsigned long atlas::constants::charBits = std::numeric_limits<unsigned char>::digits

Explanation: the constant charBits is in fact 8 everywhere. Fokko's surprise is about getting 7 for <char>, which is apparently signed Definition at line 36 of file constants.h. Referenced by atlas::constants::init().

const unsigned long atlas::constants::firstCharMask = (1ul << charBits) - 1ul

bit mask for lower order char of an unsigned long Definition at line 53 of file constants.h.

const unsigned long atlas::constants::hiBit = 1ul << (longBits - 1)

Definition at line 48 of file constants.h.

const unsigned long atlas::constants::longBits = std::numeric_limits<unsigned long>::digits

32 or 64, depending on the architecture Definition at line 41 of file constants.h. Referenced by atlas::constants::init().

const unsigned long atlas::constants::posBits = longBits - 1ul

Constant used to pick a bit-address apart: serves as flags for the address within a word. It is assumed that the number of bits in an unsigned long is a power of two. Definition at line 99 of file constants.h. Referenced by atlas::bitmap::BitMap::BitMap(), and atlas::bitmap::BitMap::set_capacity().

const size_t atlas::constants::RANK_MAX = 16ul

RANK_MAX is the largest allowed rank for a reductive group. It should not exceed 128, or the data type for Weyl groups will overflow (in a way requiring fundamental rewriting of bitSet and bitVector). It should always be a power of two. The constant PRIMES_MAX in size.h has to be set in accordance with RANK_MAX, so that Weyl group sizes can be properly stored. Definition at line 85 of file constants.h. Referenced by atlas::interactive_lietype::checkLieType(), and atlas::interactive_lietype::printRankMessage().

const unsigned long atlas::constants::sizeBits = std::numeric_limits<size_t>::digits

equal to longBits virtually everywhere Definition at line 46 of file constants.h. Referenced by atlas::pool::Pool::memoryReport(), atlas::pool::Pool::Pool(), and atlas::pool::Pool::reportDestruction().

const unsigned char atlas::constants::ucharMax = std::numeric_limits<unsigned char>::max()

Definition at line 24 of file constants.h.

const unsigned long atlas::constants::ulongMax = std::numeric_limits<unsigned long>::max()

2**32 - 1 on Mac. Definition at line 28 of file constants.h.

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